Originally Posted by D1coach

Took my car to dealer with what I thought was an alternator problem. The battery would run down and go dead even though it is only six months old. The problem turned out to be the alternator/starter/battery wiring harness, which I understand is a common problem on 05’s. The replacement harness is supposed to be heavier and not so susceptible to failure from heat as the original. The bill is close to $1500, luckily I have the aftermarket warranty. Mileage is 45,000.

From Suncoast website:

Updated Battery / Starter / Alternator Harness
Per Porsche's technical bulletin.

Issue: Battery discharged and/or will not charge properly. Voltage drop due to alternator-starter-battery harness damage at starter terminal. This issue is often mis-diagnosed as a bad battery, bad alternator, or bad starter, and these parts are often replaced in multiple repair attempts before the harness is determined to be the cause of the issue.

Fits all Carrera & Carrera S models, 2005-08.

Originally Posted by mgordon18

How does this problem get diagnosed at the dealer? Is it something you have to "prove" to them by reproducing the symptoms, or can they simply look at the harness and see that it's no good?